1. Field
The disclosed embodiments relate to substrate transport apparatus and, more particularly, to substrate transport apparatus that are configurable and interchangeable.
2. Brief Description of Related Developments
Advances in electronics and electronic devices have been fueled by the two main prongs of consumer desires; ever more sophisticated and smaller electronics/electronic devices; at ever lower prices. To provide the sought after advances in electronics commensurate advances are desired in the manufacturing (whether facilities, tools or processes) of the electronics. The introduction and continuing expanded use of automation in fabrication of electronic devices has achieved a two fold benefit corresponding almost directly with the main consumer desires. Automated manufacturing of electronics has provided between precision and reduced cost of fabrication. The improved precision of automated manufacturing leads to the ability to increase and improve miniaturization of electronic components. Also, though having a higher one time cost, than non-automated manufacturing systems, the automated manufacturing systems may be operated on a substantially continuous basis ultimately resulting in lower manufacturing costs for the devices produced therewith. Further, the improvement in precision/accuracy of the automated manufacturing devices, over their non-automated counterparts, results in commercially significant reductions in manufacturing rejects and defects thereby again leading to lower manufacturing costs for the fabricated devices. One area of manufacturing of electronic devices that has lent itself well to using automation has been the transport apparatus, devices, also referred to as robots, handling and transporting flat panels (e.g. wafers, reticles, pelicles, flat panel displays) between various processing stations. One example of a conventional robot for use in a clean room environment is disclosed in U.S. Pat. No. 4,787,813, issued Nov. 29, 1988. The conventional robot disclosed therein has a drive system with a support assembly. A first arm of the robot is rotatably supported by the support assembly and is raised and lowered by the support assembly. Drive structure for rotating the support assembly is mounted on a base. Drive structure for rotating a second arm and end effector are mounted at the upper end of the support assembly. U.S. Pat. No. 6,634,851, issued Oct. 21, 2003 discloses another example of a conventional workpiece handling robot that has a base and backbone. The base of this conventional robot has a linear drive system and a mast on the linear drive system. A shoulder drive system rotates the mast and proximal arm link mounted to the mast. An elbow drive is mounted to the proximal link for rotating a distal link relative to the proximal link. The conventional robot has an end effector that is slaved. As may be realized, the aforementioned conventional robot has limited freedom of movement as it lacks a drive system, or an independent drive axis, for independently driving the robot end effector. Nor can this conventional robot be readily configured to provide a robot configuration wherein the end effector is independently movable. The aforementioned conventional robots are exemplary of conventional robots in general. Each robot is specifically configured for a particular arrangement. Moreover, once the robot configuration is set, the configuration is substantially fixed and non-variable in major respects. In effect the conventional robots cannot be reconfigured without substantially tearing down the robot and rebuilding it anew. This limits the interchangeability and interoperability of conventional robots and results in FAB operators having many generally similar yet not interchangeable robots. By way of example, a FAB operator may have conventional 3 axes, 4 axes and 5 axes robots (each for a corresponding processing station or tool where a 3 axes, 4 axes or 5 axes robot is appropriate). Although generally similar in configuration (e.g. the conventional robots are all scara type), nevertheless the conventional 3 axes, 4 axes and 5 axes are not interchangeable, and reconfiguring of the conventional robot (e.g. configuring a 3 axes conventional robot to 5 axes or vice versa) involves complete tear down and rebuilding of the conventional robot. Hence, if a conventional robot (e.g. 3 axes) is brought off line, such as for maintenance, and a spare conventional robot with a different configuration is available (e.g. 4 axes), the spare conventional robot with the different configuration is not swappable with the offline robot nor can the spare robot be reconfigured so that it may become swappable with the offline robot. Accordingly, in the case of conventional robots production at the process stations served by the offline robot remains stopped until the offline robot is restored, or the FAB operator acquires another robot with the same configuration. This is highly undesirable.
Another problem of conventional robots, as may be realized from the aforementioned examples, is that the robots movement definition (e.g. the difference between the true position of a desired point/location on the robot and the expected position of the same point commanded by the robot controller) is rather limited. Though this limited movement definition may arise from a number of factors, one large contributing factor are undefined robot motions (robot movements that are not sensed and registered by the robot controller). One cause of undefined robot motions is the flexibility of the robot (i.e. its structure or drive system), and the foundation supporting the robot due to dynamic loads. The exemplary embodiments of the present invention overcome these and other problems of conventional workpiece fabrication systems as will be described below.